It is common knowledge that beer was produced by the ancient Egyptians and that van Leeuwenhoek (1632-1723) was the first to see yeast cells. However, what was defined as yeast in the seventeenth century is different from that of today. So did van Leeuwenhoek really observe yeast? In attempting to answer this question it might be helpful to describe some fundamental work on yeast by Charles Cagnard-Latour (1777-1859) published in 1838. (Recall that the cell theory dates from 1839). This tells us of the beer brewing and wine making state of the art around that time. It was known that the addition of yeast to properly treated grains of cereals would produce alcohol and carbon dioxide from the extracted malt sugars. In the times of van Leeuwenhoek yeast was considered an inanimate paste with no connection to living cells. What did Cagnard-Latour see? It is important to use the term “see” because, as he emphasized, he wished to approach yeast research in a new way, that is, by employing a microscope. (This approach was also followed by F. T. Kützig and Th. A. Schwann at the same time.)